An investigation by the Kent County Sheriff’s Department determined Shoemaker’s equipment was working properly.

Two divers with Shoemaker noticed him in distress when he surfaced about 150 feet from the west bank of the river. He he did not have his oxygen regulator in his mouth, the men, who were on shore, told police. Shoemaker was pulled back into the water.

His friends were unable to rescue him from the turbulent waters. Rescuers were called about 10 minutes later, police said.

Responding officers observed that Shoemaker became caught in the recirculating hydraulic of the dam. He was apparently unconscious. His regulator was not in his mouth, and his mask was displaced, police said.

He was surveying underwater areas near the dam on Saturday to help further the Grand Rapids Whitewater project. He had gone diving in the area in July without incident. The two divers accompanied him Saturday to assist and "keep an eye on him."

The Whitewater project, a $27 million proposal to remove the downtown dams and restore rapids to the river, was close to Shoemaker's heart, friends said.

Police said the divers did not receive permission from the City of Grand Rapids to conduct a diving operation, which is required by city ordinance. The Grand Rapids City Attorney’s Office determined that no charges will be brought against the two other divers.

Angie Jackson covers public safety and breaking news for MLive/The Grand Rapids Press. Email her at ajackso3@mlive.com, and follow her on Twitter.